Tracking number plate from vehicle using

International Journal in Foundations of Computer Science & Technology (IJFCST), Vol.4, No.3, May 2014
DOI:10.5121/ijfcst.2014.4304 43
TRACKING NUMBER PLATE FROM VEHICLE USING
MATLAB
Manisha Rathore and Saroj Kumari
Department of Information Technology, Banasthali University, Jaipur, India
ABSTRACT
In Traffic surveillance, Tracking of the number plate from the vehicle is an important task, which demands
intelligent solution. In this document, extraction and Recognization of number plate from vehicles image
has been done using Matlab. It is assumed that images of the vehicle have been captured from Digital
Camera. Alphanumeric Characters on plate has been Extracted and recognized using template images of
alphanumeric characters.
This paper presents a new algorithm in MATLAB which has been used to extract the number plate from the
vehicle in various luminance conditions. Extracted image of the number plate can be seen in a text file for
verification purpose. Number plate identification is helpful in finding stolen cars, car parking management
system and identification of vehicle in traffic.
KEYWORDS
Number plate Extraction, MATLAB, Recognization, Digital Camera, luminance condition.
1. INTRODUCTION
Number plate extraction is hotspot research area in the field of image processing. Many of
automated system have been developed but each has its advantages and disadvantages. It is
assumed that this algorithm worked on images which have been captured from fixed angle
parallel to horizon in different luminance conditions. It is also assumed the vehicle is stationary
and images are captured at fixed distance.
An automated system is developed using MATLAB in which image is captured from camera and
converted in Gray scale image for pre processing. After conversion, dilation process is applied on
image and unwanted holes in image have been filled. After dilation, horizontal and vertical edge
processing of has been done and passed these histograms through low pass filters. Low pass
filters filter out unwanted regions or unwanted noise from image. After this filtering, image is
segmented and region of interest is extracted and image is converted into binary form. Binary
images are easily processed as compared to coloured images. After Binarization, each
alphanumeric character on number plate is extracted and then recognized with the help of
template images of alphanumeric characters. After this, each alphanumeric character is stored in
file and whole number plate is extracted successfully.
The paper is organized as follows: Section 2 presents literature survey of number plate extraction
Section 3 presents the proposed methodology for number plate extraction. Section 4 presents the
experimental results. Section 5 shows result. Section 6 draws conclusion.

44
2. LITERATURE SURVEY
Chittode J S et al. [1] developed algorithm which is applied on the car park systems to monitor
and manage parking services. Algorithm is developed on the basis of morphological operations
and used for number plate recognition. Optical character is used for the recognition of characters
in number plate.
Peng H et al. [2] presented an algorithm named “Document Image Recognition”. DIR is most
effective approach which is used to find most similar template for input image in a database. The
algorithm is developed on the basis of global matching of CBP Chunyu C et al. [3] presented a
technique for recognition of number plate from vehicle image. This technique is implemented
using MATLAB and characters are recognized using edge detection segmentation and pre
processing of image.
Lekhana G.C et al. [4] developed an efficient real time on-line Number plate recognition system.
NPR algorithm works in different steps firstly image acquisition, using fusion of spectral analysis
characters are segmented and characters are recognized.
Paunwala C.N et al. [5] proposed a methodology which finds ROI using morphological
processing and directional segmentation. The ROI is the area which includes the number plate
from which alphanumeric characters are recognized. This method is tested on different databases
which contain images.
Singh M et al. [6] developed an efficient approach works on opening and closing of
morphological operations. Firstly localization of plate in image has been done then skew
correction is done for segmentation process of alphanumeric characters. Recognization is done
using the template matching.
Kranti S et al. [7] presented a methodology for number plate extraction named “Feature based
number plate localization “. This methodology mainly deals on two methods edge detection and
window filtering method. Both methods are used in this methodology and give efficient results.
Ganapathy V et al. [8] developed a methodology for Malaysian vehicles. This methodology is
mainly based on Hough transform and morphological analysis and results extraction of number
plate with 95% accuracy.
Othman K et al. [9] used an approach which is texture based approach and worked on edge
information for localization and recognition. Multi layer perceptron and neural network are used
for segmentation of alphanumeric characters of license plate.
3. METHODOLOGY
Methodology is shown in flowchart. Step by step process is followed for pre processing of image.
MATLAB provides all image processing function and toolbox. MATLAB have large library
functions and set of tools.
Main features of MATLAB are following:
1. It provides advanced algorithm for high numerical computation.
2. Ability to define user define functions and large collection of mathematical functions.
3. For plotting and displaying data, two and three dimensional graphics are supported.
4. Online help is present which is very much helpful for new user.

45
5. Powerful, effective and efficient matrix and vector oriented high level programming
language is provided by MATLAB.
6. Several toolboxes are provides for solving domain specific problems. Some of toolboxes
are Image processing toolbox. Fuzzy logic, Digital signal processing toolbox, neural
network toolbox etc.
Figure 1. Flowchart
Step 1: Image Acquisition
In this step image is captured from digital camera. Image should be taken from fixed angle
parallel to horizon. Vehicle should be stationary. Input image is shown in figure2.

46
Figure 2. Input Image
Step 2: Convert into Gray image
This algorithm works on Gray level image, for pre- processing and identifying the required
information. In this step coloured image is converted into the Gray scale image. Gray scale
image is shown in figure 3.
Figure 3. Gray Image
Step 3: Dilation of an Image
In this step, image has been dilated. Dilation is a process for filling holes in an image,
sharpen edges of an object maximize brightness and connect the broken lines. Dilation can
remove unwanted noise from image. Dilated image is shown in figure 4.

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Figure 4. Dilated Image
Step 4: Horizontal & Vertical edge processing
Horizontal and Vertical histogram denotes the column wise and row wise histograms.
These histograms represent the row wise and column wise sum of difference of Gray scale
values among neighbouring pixel values. Firstly, horizontal histogram is calculated by
traversing each column then vertical histogram is calculated by traversing each row.
Step 5: Passing histograms through low pass filter
Histogram values are passed through low pass filter because values of histogram between
consecutive row and column changes drastically, to minimize loss of information smooth
out changes. In this step histogram value is averaged out among both sides. This step is
performed for both horizontal and vertical histograms. Filtering removes all the unwanted
regions of an image. Passing histogram through low pass filter is shown in figure 5 and 6.
Figure5. Vertical Edge processing

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Figure 6. Horizontal Edge Processing
Step 6: Segmentation of Region of Interest
Image has been segmented. In this step all the regions which have probability of license
plate has been identified and coordinates of such probable region has been stored. The
following figure shows the segmented region. The segmented regions are shown in fig7.
Figure7. Segmented Image
Step 7: Extraction of region of interest
From above segmented image, region with maximum histogram value is taken as the most
probable region for number plate. Among all the regions, the region with highest horizontal
and vertical histogram value is identified. This region is considered as highest possibility of
containing number plate and is extracted shown in figure 8.

49
Figure 8. Extracted Image
Step 8: Convert into Binary Image
Image is converted into binary image from Gray scale. Intensity change value is calculated
easily as compared to Gray scale and colour image. Binary image is shown in figure 9.
Figure9. Binary image of extracted image
Step 9: Segmentation of alphanumeric character
Individual alphanumeric characters are segmented. Segmentation has been done by using
smearing algorithms in both horizontal and vertical histogram. For filling space of inner part
of each character the vertical smearing algorithm is applied and some threshold value is
determined. Similarly, horizontal smearing algorithm is applied. Each individual
alphanumeric character is extracted by finding starting and ending points of character in
horizontal direction. These characters are shown in figure 10.

50
Figure10. Extracted characters from number plate
Step 10: Recognization of individual character
For Recognization of individual alphanumeric character, template based Recognization
method is used. In template based algorithm, segmented image is compared with one image
which is stored in database named as template image. In both images best matched similarity
is compared. This similarity is matched with statistical method correlation. The image for
which the correlation coefficient for template image is maximum that image is best matched.
These template images are shown in figure 11.
Figure 11. Template Images
Step 11: Storing in file
After extracting, number plate is stored in file with complete information like characters on
number plate and date on which it is extracted. This shown in figure 12

51
Figure 12. Extracted plate is stored in file.
4. RESULT
The system works with 99% accuracy when images are captured from fixed distance and
captured from the centre position. Vehicle should be stationary and image is captured from fixed
angle parallel to horizon. Car number plate should be according to 1989 motor vehicle limited.
There are few problems where system does not work, these figures are shown figure 13. In these
figure either the system does not extract number plate from Gray scale due to some luminance
conditions or due to problematic backgrounds.

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Figure13. Problematic images where number plate is not extracted
5. CONCLUSION
Number plate extraction needs extremely high accuracy when working on images of busy
roads or parking areas. This system gives about 90% of efficiency and has been tested
with nearly 40 vehicles.
REFERENCES
[1] J.S. Chittode and R. Kate, “Number plate recognition using segmentation,” International Journal of
Engineering Research & Technology, Vol. 1 Issue 9, November- 2012.
[2] H. Peng, F. Long and Z. Chi, “Document image recognition based on template matching of
component block projections,” IEEE transaction on Pattern Analysis and machine Intelligence, Vol.
25, no. 9, pp 1188-1192, sep 2003.
[3] C. Chunyu, W. Fucheng, C. Baozhi and Z. Chen,” Application of image processing to the vehicle
license plate recognition,” International Conference on Computer Science and Electronics
Engineering, published by Allantis press, pp 2867-2869, 2013.
[4] G. C.Lekhana and R.Srikantaswamy,” Real time license plate recognition system,” International
Journal of Advanced Technology & Engineering Research, Vol-2, Issue-4, pp 5-9, July 2012.
[5] C N Paunwala and S Patnaik, ”A novel multiple license plate extraction technique for complex
background in Indian traffic conditions,” International Journal of Image processing, Vol-4,Issue-2,pp
106-118.
[6] Pandya and M Sing,” Morphology based approach to recognize number plates in India,” International
Journal of Soft Computing and Engineering,Vol-1, Issue-3, pp 107-113, June2011.
[7] S Kranti and K Pranathi,” Automatic number plate recognition,” International Journal of
Advancements in Technology,vol-2, no-3, pp408-423, July 2011.
[8] V Ganapathy and W.L.D Lui,” A Malaysian vehicle license plate localization and recognition
system,” Journal of Systemic and Cybernetics (pdf from freewebs.com)
[9] O Khalifa, S Khan, R Islam and A Suleiman,” Malaysian vehicle license plate recognition,” The
International Arab Journal of Information Technology, vol-4, no-4, pp 359-365, Oct 2007.

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Authors
Manisha Rathore is an active researcher in the field of image processing, currently
studying in M.Tech (IT) from Banasthali University.
Saroj Kumari is an active researcher in the field of image processing, currently studying
in M.Tech (IT) from Banasthali University.

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